1. Field of the Invention
The present invention relates to a wireless network printer. More particularly, the present invention relates to a method for performing network scanning that changes a scanning operation according to whether the wireless network printer establishes a link and performs a specific operation, and an apparatus using the method.
2. Description of the Related Art
A wireless network device, such as a wireless network printer, can communicate with another wireless network device through a wireless network. FIG. 1 is a block diagram illustrating a conventional wireless network module. Referring to FIG. 1, the wireless network printer comprises the wireless network module 100 or a wireless network card in order to communicate with another wireless network device, such as a computer. The wireless network module 100 comprises a CPU 110, a read-only memory (ROM) 112, a random-access memory (RAM) 114, a non-volatile memory (NVRAM) 116, an input/output interface unit 118, and a wireless communication module 120. The CPU 110 controls the wireless network module 100. The ROM 112, RAM 114, and NVRAM 116 store programs or data. The input/output interface unit 118 communicates with an external peripheral device. The wireless communication module 120 communicates with another wireless network device though a wireless network 130. The wireless network 130 includes an 802.11b network 132, an 802.11g network 134, and an 802.11a network 136 based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless network standard.
The wireless network printer enters an operation mode in order to communicate with another wireless network device. The operation mode includes an infrastructure mode or an ad-hoc mode. FIG. 2 illustrates the network configuration when in ad-hoc mode, and FIG. 3 illustrates the network configuration when in infrastructure mode.
Referring to FIG. 2, a wireless network printer 10 in the ad-hoc mode is directly connected to a peripheral wireless network device, such as a notebook computer 22 or a computer 24. Referring to FIG. 3, the wireless network printer 10 in the infrastructure mode is connected to the peripheral wireless network device, such as a notebook computer 38 through an access point (AP) 30, or connected to wired computers 32, 34, and 36 through the AP 30.
A set point relating to a wireless local area network (LAN) such as a service set identifier (SSID) and wired equivalent privacy (WEP) must be established in the wireless network printer, in order for it to communicate with another wireless network device.
The wireless network device such as the wireless network printer is referred to as a wireless station. The wireless station also includes the AP and the wireless network device such as a computer and a printer.
The wireless station performs a scanning operation, thereby searching and connecting to a peripheral network, and informs a user of the search result, so that the user can more easily select and connect to the most suitable network for the wireless station. A wireless LAN scan includes an active scan and a passive scan. The active scan is used to directly transmit a probe request packet to a station, and receive a probe response packet in response to the probe request packet. The passive scan is used to receive a beacon frame only when the station transmits the beacon frame.
The wireless station such as the computer and the printer using the wireless LAN searches for a peripheral network according to a user's instructions or automatically, and informs the user of any network found. The active scan performed at the request of the user transmits a probe packet, and receives a probe response from stations capable of responding to the probe packet in order to notify the station of what wireless network exists around the station. Such an operation is performed for each of a number of channels. In IEEE 802.11b, each of fourteen channels transmits the probe request packet, and receives the probe response packet. The probe request packet includes information such as a basic service set identifier (BSSID), the WEP, the time, or the like. The station determines signal sensitivity by receiving packets along with channel information. When the user requests the station to search for the peripheral network, the station performs the above process and informs the user of the result as shown in Table 1.
TABLE 1No.SSIDOperationWEPBSSIDSignal1SamsungInfrastructureoff0x000f0a0123490%2PrinterInfrastructureon0x000f0a0123570%3Airportthruad-hocoff0x02350a0123450%
FIG. 4 illustrates the scanning operations of a wireless network system. Referring to FIG. 4, the active scanning operation will now be described in more detail. When the station is in the infrastructure mode or the ad-hoc mode, the station transmits the probe request packet in each channel, first and second APs 48 and 50 or first and second ad-hoc stations 42 and 46 of the corresponding channel respond to the probe request packet. When a first infrastructure station 44 or a second infrastructure station 40 transmits the probe request packet, the first and second APs 48 and 50 or the first and second ad-hoc stations 42 and 46 respond to the probe request packet.
The passive scan is not performed at the request of the user, but the station receives the beacon frame periodically generated from the AP or the ad-hoc station in each channel to collect information. The beacon frame includes a time stamp, the SSID, a beacon interval, capability information, and the like, which are used to obtain the result as shown in Table 1.
Although the active scan can search the peripheral network faster than the passive scan, the active scan consumes more power than the passive scanning, since the active scanning method requires that the station transmit the probe request packet.
In the active scanning method, after the station transmits the probe request packet, it must stand by for a predetermined time until it receives a response, and is not able to normally perform communication during that time. This is because the station collects information while changing between a plurality of channels. An initialized station or a network client such as the computer can perform the active scan at a time desired by the user. However, since a network server such as a printer must stand by for a request from the network client at all times, active scanning by the network server causes periodic disconnection problems. Moreover, when a wireless network card supporting all the IEEE 802.11a/b/g standards is used to perform the active scan, it causes a disconnection problem for up to several minutes. Since the passive scanning method requires the station to stand by for the predetermined time until it receives the beacon frame, it also causes disconnection problems.
A channel scanning method and a channel scanning system in a wireless network are disclosed in U.S. Patent Application Publication No. 2004/0137905, the entire disclosure of which is hereby incorporated by reference.
Accordingly, there is a need for method and apparatus for passively and actively scanning a network device without causing a disconnection problem.